1. Field of the Invention
The present invention relates to a sliding module for a sliding-type portable terminal, which is adapted to provide one side of a sliding-type housing with dual elastic force for smooth sliding operation.
2. Description of the Related Art
In general, “portable communication apparatus” refers to an electronic apparatus that a user can carry to perform wireless communication. Portable communication apparatuses may be classified into various categories according to their appearance, such as bar-type apparatuses, flip-type apparatuses, and folder-type apparatuses. The bar-type apparatuses have a single housing shaped like a bar. The flip-type apparatuses have a flip rotatably coupled to a bar-shaped housing by a hinge device. The folder-type apparatuses have a folder connected to a single bar-shaped housing by a hinge device so that the folder can be rotated to fold on or unfold from the housing.
In addition, portable communication apparatuses may be classified into rotation-type apparatuses and sliding-type apparatuses according to the manner of opening and closing them. In the rotation-type apparatuses, two housings are coupled to each other so that one housing rotates to be opened or closed relative to the other while they face each other. In the sliding-type apparatuses, two housings are coupled to each other so that one housing slides along a longitudinal direction to be opened or closed relative to the other housing. These variously classified portable communication apparatuses can be easily understood by those skilled in the art.
Referring to FIGS. 1 to 5, a conventional sliding-type portable terminal 1 includes a main body 2, a number of keypads 2a positioned on the main body 2, a microphone device 2b positioned on the main body 2, and a sliding body 3 adapted to slide a distance corresponding up to half the length of the main body 2 in the upward or downward direction so as to expose the main body 2. The main body 2 is usually provided with a 3×4 keypad. On the front surface of the sliding body 3, an auxiliary keypad composed of a number of auxiliary keys, a speaker device 3a, and a display device 3b may be positioned.
More particularly, referring to FIGS. 1-4, a conventional sliding-type portable terminal 1 includes a main body 2, a sliding body 3 adapted to slide up to a predetermined distance on the main body 2, guide means 4a, 4b, 4c positioned in the main and sliding bodies 2 and 3 to guide the sliding body 3 on the main body 2, and at least one coil spring 5 positioned between the main and sliding bodies 2 and 3 to provide elastic force so that the sliding body 3 can slide upwards or downwards.
Referring to FIGS. 3 and 4, the main body 2 has a flat main plate 2c, and the sliding body 3 has a flat sliding plate 3c. 
The guide means 4 have guide ribs 4a positioned on both sides of the sliding plate 3c. The main plate 2c is provided with guide slots 4b, which are coupled to the guide ribs 4a. 
However, the conventional sliding-type portable terminal, which has a main plate in the main body, a sliding plate in the sliding body, and a torsion spring positioned between the plates so that the sliding body can slide, has a problem in that the radius of rotation of the spring and the resulting distance of movement depend on the width of the plates. More particularly, the size and thickness of the plates can hardly be reduced. This is an obstacle to making the terminal in a compact size with an aesthetic appearance.
Furthermore, the terminal has a flexible circuit, which is connected to an LCD, and a torsion spring on the central portion. The flexible circuit and the torsion spring may interfere with and damage each other. In addition, the fact that the flexible circuit and the torsion spring overlap each other increases the thickness of the terminal and adversely affects the slimness.
U.S. Pat. No. 6,822,871 commonly assigned to the assignee of the present application discloses a sliding-type portable communication apparatus, which includes two housings having a predetermined thickness, as well as a flexible circuit and a torsion spring contained in the corresponding housings. This construction has a problem in that the vertical dimension of the terminal, i.e. the thickness, inevitably increases. This adversely affects the slimness and provides users with a poor grip. In addition, the exterior design is limited to a large extent.